Messages in this thread |  | | | Date | Mon, 27 Apr 2009 13:12:52 -0700 | | From | David Hawkins <> | | Subject | Re: [PATCH] fsldma: use PCI Read Multiple command |
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>>>> Can you give me an example of non-PCI memory that would be >>>> non-prefetchable that you'd like us to try? We can see if our >>>> host CPUs have an area like that ... we just need to know >>>> what device to look for first :) >>> You can mark the pci inbound window on the 83xx as non-prefetchable >>> (assuming 83xx is host). On a x86 host I doubt there is any easy way >>> to get non-prefetchable memory. >> >> Yep, we were going to do that, but chose to use the >> 1MB region already setup for the IMMRs since its already >> marked as non-prefetchable. We were only doing reads, so >> it wasn't going to hurt anything. >> >> I doubt that marking one of the other BAR regions >> as non-prefetchable will give a different result. >> However, we're more than happy to double-check if >> you'd like. > > Its possible you'll get a different result since IMMR is a register > space internal and thats normally a completely different bus than memory > would be (internal to the 83xx). I'd suggest double-checking w/a BAR > marked non-prefetch pointing to real memory.
We had a 4k BAR1 setup to point to DDR memory.
With prefetchable set, a 36-byte transfer generated a burst-of-8 32-bit words followed by a single transaction.
With non-prefetchable set, the transfers were all single.
So it works like we'd expect.
Cheers, Dave
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